Final answer:
The terminator in a transcriptional unit in bacteria functions to signal the end of transcription, triggering the release of the newly made mRNA from the DNA template.
Step-by-step explanation:
The function of the terminator in a transcriptional unit in bacteria is to signal the end of transcription. During the transcription process, prokaryotic RNA polymerase must be instructed to release the newly made mRNA. This occurs when the polymerase encounters specific sequences in the DNA template that act as termination signals.
These signals can be either protein-based, known as Rho-dependent termination, or RNA-based, known as Rho-independent termination. In Rho-dependent termination, the rho protein causes the polymerase to dissociate from the DNA when it stalls at a run of guanine (G) nucleotides. For Rho-independent termination, the formation of a stable stem-loop structure called the terminator or terminator stem in the mRNA prompts the release of the RNA polymerase and the mRNA transcript from the DNA template.